var fibonacci = (n)=>{
    if(typeof n !== 'number'){
        throw new Error('n should be a Number')
    }
    if(n<0){
        throw new Error('n should >= 0')
    }
    if(n>10){
        throw new Error('n should <= 10')
    }
    if(n===0){
        return 0;
    }
    if(n===1){
        return 1;
    }

    return fibonacci(n-1)+fibonacci(n-2);
}

exports.fibonacci = fibonacci;

if(require.main===module){
    var n = Number(process.argv[2]);
    console.log('fibonacci( '+n+' ) is',fibonacci(n))
}